Wireless communication devices have become smaller and more powerful as well as more capable. Increasingly users rely on wireless communication devices for mobile phone use as well as email and Internet access. At the same time, devices have become smaller in size. Devices such as cellular telephones, personal digital assistants (PDAs), laptop computers, and other similar devices provide reliable service with expanded coverage areas. Such devices may be referred to as mobile stations, stations, access terminals, user terminals, subscriber units, user equipments, and similar terms.
A wireless communication system may support communication for multiple wireless communication devices at the same time. In use, a wireless communication device may communicate with one or more base stations by transmissions on the uplink and downlink. Base stations may be referred to as access points, Node Bs, or other similar terms. The uplink or reverse link refers to the communication link from the wireless communication device to the base station, while the downlink or forward link refers to the communication from the base station to the wireless communication devices.
Wireless communication systems may be multiple access systems capable of supporting communication with multiple users by sharing the available system resources, such as bandwidth and transmit power. Examples of such multiple access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, wideband code division multiple access (WCDMA) systems, global system for mobile (GSM) communication systems, enhanced data rates for GSM evolution (EDGE) systems, and orthogonal frequency division multiple access (OFDMA) systems.
In a receiver, such as a wireless receiver, desired signals may be blocked due to an adjacent high strength signal. This strong signal may saturate the receive circuitry and block the weaker primary receive signal. This occurs when the front end receive circuitry and automatic gain control (AGC) react to the stronger signal, and reduce the front end amplification. When this happens, the desired primary channel receive signal may be lost in the background noise.
Transmit jammer leakage may be a powerful blocker for the receive path in frequency duplex division (FDD) mode in many bands of a wireless communication system, such as the long-term evolution (LTE) band. In the LTE bands receive spacing may be as little as a few tens of MHz. This spacing leads to receiver front end design challenges as filtering of near end blockers in RF is made nearly impossible due to the lack of high quality (Q) of chip components. In addition to generating nonlinearity components the transmit jammer may saturate the first stage of the base band (BB) filter in high gain modes in the presence of weak signals, as described above. Common filtering techniques such as RC filtering is less effective because the rejection is only a few dBs. Thus, there is a need in the art for a method and apparatus to reject near end blockers and transmit leakage.